#=======================================================================
#
#	 Python Lexical Analyser
#
#	 Regular Expressions
#
#=======================================================================

import array
import string
import types
from sys import maxint

import Errors

#
#	 Constants
#

BOL = 'bol'
EOL = 'eol'
EOF = 'eof'

nl_code = ord('\n')

#
#	 Helper functions
#

def chars_to_ranges(s):
  """
  Return a list of character codes consisting of pairs
  [code1a, code1b, code2a, code2b,...] which cover all
  the characters in |s|.
  """
  char_list = list(s)
  char_list.sort()
  i = 0
  n = len(char_list)
  result = []
  while i < n:
    code1 = ord(char_list[i])
    code2 = code1 + 1
    i = i + 1
    while i < n and code2 >= ord(char_list[i]):
      code2 = code2 + 1
      i = i + 1
    result.append(code1)
    result.append(code2)
  return result

def uppercase_range(code1, code2):
  """
  If the range of characters from code1 to code2-1 includes any
  lower case letters, return the corresponding upper case range.
  """
  code3 = max(code1, ord('a'))
  code4 = min(code2, ord('z') + 1)
  if code3 < code4:
    d = ord('A') - ord('a')
    return (code3 + d, code4 + d)
  else:
    return None

def lowercase_range(code1, code2):
  """
  If the range of characters from code1 to code2-1 includes any
  upper case letters, return the corresponding lower case range.
  """
  code3 = max(code1, ord('A'))
  code4 = min(code2, ord('Z') + 1)
  if code3 < code4:
    d = ord('a') - ord('A')
    return (code3 + d, code4 + d)
  else:
    return None

def CodeRanges(code_list):
  """
  Given a list of codes as returned by chars_to_ranges, return
  an RE which will match a character in any of the ranges.
  """
  re_list = []
  for i in xrange(0, len(code_list), 2):
    re_list.append(CodeRange(code_list[i], code_list[i + 1]))
  return apply(Alt, tuple(re_list))

def CodeRange(code1, code2):
  """
  CodeRange(code1, code2) is an RE which matches any character
  with a code |c| in the range |code1| <= |c| < |code2|.
  """
  if code1 <= nl_code < code2:
    return Alt(RawCodeRange(code1, nl_code), 
               RawNewline, 
               RawCodeRange(nl_code + 1, code2))
  else:
    return RawCodeRange(code1, code2)

#
#	 Abstract classes
#

class RE:
  """RE is the base class for regular expression constructors.
  The following operators are defined on REs:

     re1 + re2		 is an RE which matches |re1| followed by |re2|
     re1 | re2		 is an RE which matches either |re1| or |re2|
  """

  nullable = 1 # True if this RE can match 0 input symbols
  match_nl = 1 # True if this RE can match a string ending with '\n'
  str = None	 # Set to a string to override the class's __str__ result
  
  def build_machine(self, machine, initial_state, final_state, 
                    match_bol, nocase):
    """
    This method should add states to |machine| to implement this
    RE, starting at |initial_state| and ending at |final_state|.
    If |match_bol| is true, the RE must be able to match at the
    beginning of a line. If nocase is true, upper and lower case
    letters should be treated as equivalent.
    """
    raise exceptions.UnimplementedMethod("%s.build_machine not implemented" % 
      self.__class__.__name__)
  
  def build_opt(self, m, initial_state, c):
    """
    Given a state |s| of machine |m|, return a new state
    reachable from |s| on character |c| or epsilon.
    """
    s = m.new_state()
    initial_state.link_to(s)
    initial_state.add_transition(c, s)
    return s

  def __add__(self, other):
    return Seq(self, other)

  def __or__(self, other):
    return Alt(self, other)

  def __str__(self):
    if self.str:
      return self.str
    else:
      return self.calc_str()

  def check_re(self, num, value):
    if not isinstance(value, RE):
      self.wrong_type(num, value, "Plex.RE instance")

  def check_string(self, num, value):
    if type(value) <> type(''):
      self.wrong_type(num, value, "string")
  
  def check_char(self, num, value):
    self.check_string(num, value)
    if len(value) <> 1:
      raise Errors.PlexValueError("Invalid value for argument %d of Plex.%s."
        "Expected a string of length 1, got: %s" % (
          num, self.__class__.__name__, repr(value)))

  def wrong_type(self, num, value, expected):
    if type(value) == types.InstanceType:
        got = "%s.%s instance" % (
          value.__class__.__module__, value.__class__.__name__)
    else:
      got = type(value).__name__
    raise Errors.PlexTypeError("Invalid type for argument %d of Plex.%s "
                    "(expected %s, got %s" % (
                      num, self.__class__.__name__, expected, got))
  
#
#	 Primitive RE constructors
#	 -------------------------
#
#	 These are the basic REs from which all others are built.
#

## class Char(RE):
##	 """
##	 Char(c) is an RE which matches the character |c|.
##	 """
  
##	 nullable = 0
  
##	 def __init__(self, char):
##		 self.char = char
##		 self.match_nl = char == '\n'
    
##	 def build_machine(self, m, initial_state, final_state, match_bol, nocase):
##		 c = self.char
##		 if match_bol and c <> BOL:
##			 s1 = self.build_opt(m, initial_state, BOL)
##		 else:
##			 s1 = initial_state
##		 if c == '\n' or c == EOF:
##			 s1 = self.build_opt(m, s1, EOL)
##		 if len(c) == 1:
##			 code = ord(self.char)
##			 s1.add_transition((code, code+1), final_state)
##			 if nocase and is_letter_code(code):
##				 code2 = other_case_code(code)
##				 s1.add_transition((code2, code2+1), final_state)
##		 else:
##			 s1.add_transition(c, final_state)

##	 def calc_str(self):
##		 return "Char(%s)" % repr(self.char)

def Char(c):
  """
  Char(c) is an RE which matches the character |c|.
  """
  if len(c) == 1:
    result = CodeRange(ord(c), ord(c) + 1)
  else:
    result = SpecialSymbol(c)
  result.str = "Char(%s)" % repr(c)
  return result

class RawCodeRange(RE):
  """
  RawCodeRange(code1, code2) is a low-level RE which matches any character
  with a code |c| in the range |code1| <= |c| < |code2|, where the range
  does not include newline. For internal use only.
  """
  nullable = 0
  match_nl = 0
  range = None					 # (code, code)
  uppercase_range = None # (code, code) or None
  lowercase_range = None # (code, code) or None
  
  def __init__(self, code1, code2):
    self.range = (code1, code2)
    self.uppercase_range = uppercase_range(code1, code2)
    self.lowercase_range = lowercase_range(code1, code2)
  
  def build_machine(self, m, initial_state, final_state, match_bol, nocase):
    if match_bol:
      initial_state = self.build_opt(m, initial_state, BOL)
    initial_state.add_transition(self.range, final_state)
    if nocase:
      if self.uppercase_range:
        initial_state.add_transition(self.uppercase_range, final_state)
      if self.lowercase_range:
        initial_state.add_transition(self.lowercase_range, final_state)
  
  def calc_str(self):
    return "CodeRange(%d,%d)" % (self.code1, self.code2)

class _RawNewline(RE):
  """
  RawNewline is a low-level RE which matches a newline character.
  For internal use only.
  """
  nullable = 0
  match_nl = 1

  def build_machine(self, m, initial_state, final_state, match_bol, nocase):
    if match_bol:
      initial_state = self.build_opt(m, initial_state, BOL)
    s = self.build_opt(m, initial_state, EOL)
    s.add_transition((nl_code, nl_code + 1), final_state)

RawNewline = _RawNewline()


class SpecialSymbol(RE):
  """
  SpecialSymbol(sym) is an RE which matches the special input
  symbol |sym|, which is one of BOL, EOL or EOF.
  """
  nullable = 0
  match_nl = 0
  sym = None

  def __init__(self, sym):
    self.sym = sym

  def build_machine(self, m, initial_state, final_state, match_bol, nocase):
    # Sequences 'bol bol' and 'bol eof' are impossible, so only need
    # to allow for bol if sym is eol
    if match_bol and self.sym == EOL:
      initial_state = self.build_opt(m, initial_state, BOL)
    initial_state.add_transition(self.sym, final_state)


class Seq(RE):
  """Seq(re1, re2, re3...) is an RE which matches |re1| followed by
  |re2| followed by |re3|..."""

  def __init__(self, *re_list):
    nullable = 1
    for i in xrange(len(re_list)):
      re = re_list[i]
      self.check_re(i, re)
      nullable = nullable and re.nullable
    self.re_list = re_list
    self.nullable = nullable
    i = len(re_list)
    match_nl = 0
    while i:
      i = i - 1
      re = re_list[i]
      if re.match_nl:
        match_nl = 1
        break
      if not re.nullable:
        break
    self.match_nl = match_nl
    
  def build_machine(self, m, initial_state, final_state, match_bol, nocase):
    re_list = self.re_list
    if len(re_list) == 0:
      initial_state.link_to(final_state)
    else:
      s1 = initial_state
      n = len(re_list)
      for i in xrange(n):
        if i < n - 1:
          s2 = m.new_state()
        else:
          s2 = final_state
        re = re_list[i]
        re.build_machine(m, s1, s2, match_bol, nocase)
        s1 = s2
        match_bol = re.match_nl or (match_bol and re.nullable)

  def calc_str(self):
    return "Seq(%s)" % string.join(map(str, self.re_list), ",")


class Alt(RE):
  """Alt(re1, re2, re3...) is an RE which matches either |re1| or
  |re2| or |re3|..."""

  def __init__(self, *re_list):
    self.re_list = re_list
    nullable = 0
    match_nl = 0
    nullable_res = []
    non_nullable_res = []
    i = 1
    for re in re_list:
      self.check_re(i, re)
      if re.nullable:
        nullable_res.append(re)
        nullable = 1
      else:
        non_nullable_res.append(re)
      if re.match_nl:
        match_nl = 1
      i = i + 1
    self.nullable_res = nullable_res
    self.non_nullable_res = non_nullable_res
    self.nullable = nullable
    self.match_nl = match_nl

  def build_machine(self, m, initial_state, final_state, match_bol, nocase):
    for re in self.nullable_res:
      re.build_machine(m, initial_state, final_state, match_bol, nocase)
    if self.non_nullable_res:
      if match_bol:
        initial_state = self.build_opt(m, initial_state, BOL)
      for re in self.non_nullable_res:
        re.build_machine(m, initial_state, final_state, 0, nocase)

  def calc_str(self):
    return "Alt(%s)" % string.join(map(str, self.re_list), ",")


class Rep1(RE):
  """Rep1(re) is an RE which matches one or more repetitions of |re|."""

  def __init__(self, re):
    self.check_re(1, re)
    self.re = re
    self.nullable = re.nullable
    self.match_nl = re.match_nl

  def build_machine(self, m, initial_state, final_state, match_bol, nocase):
    s1 = m.new_state()
    s2 = m.new_state()
    initial_state.link_to(s1)
    self.re.build_machine(m, s1, s2, match_bol or self.re.match_nl, nocase)
    s2.link_to(s1)
    s2.link_to(final_state)

  def calc_str(self):
    return "Rep1(%s)" % self.re


class SwitchCase(RE):
  """
  SwitchCase(re, nocase) is an RE which matches the same strings as RE, 
  but treating upper and lower case letters according to |nocase|. If
  |nocase| is true, case is ignored, otherwise it is not.
  """
  re = None
  nocase = None

  def __init__(self, re, nocase):
    self.re = re
    self.nocase = nocase
    self.nullable = re.nullable
    self.match_nl = re.match_nl

  def build_machine(self, m, initial_state, final_state, match_bol, nocase):
    self.re.build_machine(m, initial_state, final_state, match_bol, 
                          self.nocase)

  def calc_str(self):
    if self.nocase:
      name = "NoCase"
    else:
      name = "Case"
    return "%s(%s)" % (name, self.re)

#
#	 Composite RE constructors
#	 -------------------------
#
#	 These REs are defined in terms of the primitive REs.
#

Empty = Seq()
Empty.__doc__ = \
  """
  Empty is an RE which matches the empty string.
  """
Empty.str = "Empty"

def Str1(s):
  """
  Str1(s) is an RE which matches the literal string |s|.
  """
  result = apply(Seq, tuple(map(Char, s)))
  result.str = "Str(%s)" % repr(s)
  return result

def Str(*strs):
  """
  Str(s) is an RE which matches the literal string |s|.
  Str(s1, s2, s3, ...) is an RE which matches any of |s1| or |s2| or |s3|...
  """
  if len(strs) == 1:
    return Str1(strs[0])
  else:
    result = apply(Alt, tuple(map(Str1, strs)))
    result.str = "Str(%s)" % string.join(map(repr, strs), ",")
    return result

def Any(s):
  """
  Any(s) is an RE which matches any character in the string |s|.
  """
  #result = apply(Alt, tuple(map(Char, s)))
  result = CodeRanges(chars_to_ranges(s))
  result.str = "Any(%s)" % repr(s)
  return result

def AnyBut(s):
  """
  AnyBut(s) is an RE which matches any character (including
  newline) which is not in the string |s|.
  """
  ranges = chars_to_ranges(s)
  ranges.insert(0, -maxint)
  ranges.append(maxint)
  result = CodeRanges(ranges)
  result.str = "AnyBut(%s)" % repr(s)
  return result

AnyChar = AnyBut("")
AnyChar.__doc__ = \
  """
  AnyChar is an RE which matches any single character (including a newline).
  """
AnyChar.str = "AnyChar"

def Range(s1, s2 = None):
  """
  Range(c1, c2) is an RE which matches any single character in the range
  |c1| to |c2| inclusive.
  Range(s) where |s| is a string of even length is an RE which matches
  any single character in the ranges |s[0]| to |s[1]|, |s[2]| to |s[3]|,...
  """
  if s2:
    result = CodeRange(ord(s1), ord(s2) + 1)
    result.str = "Range(%s,%s)" % (s1, s2)
  else:
    ranges = []
    for i in range(0, len(s1), 2):
      ranges.append(CodeRange(ord(s1[i]), ord(s1[i+1]) + 1))
    result = apply(Alt, tuple(ranges))
    result.str = "Range(%s)" % repr(s1)
  return result

def Opt(re):
  """
  Opt(re) is an RE which matches either |re| or the empty string.
  """
  result = Alt(re, Empty)
  result.str = "Opt(%s)" % re
  return result

def Rep(re):
  """
  Rep(re) is an RE which matches zero or more repetitions of |re|.
  """
  result = Opt(Rep1(re))
  result.str = "Rep(%s)" % re
  return result

def NoCase(re):
  """
  NoCase(re) is an RE which matches the same strings as RE, but treating
  upper and lower case letters as equivalent.
  """
  return SwitchCase(re, nocase = 1)

def Case(re):
  """
  Case(re) is an RE which matches the same strings as RE, but treating
  upper and lower case letters as distinct, i.e. it cancels the effect 
  of any enclosing NoCase().
  """
  return SwitchCase(re, nocase = 0)

#
#	 RE Constants
#
  
Bol = Char(BOL)
Bol.__doc__ = \
  """
  Bol is an RE which matches the beginning of a line.
  """
Bol.str = "Bol"

Eol = Char(EOL)
Eol.__doc__ = \
  """
  Eol is an RE which matches the end of a line.
  """
Eol.str = "Eol"

Eof = Char(EOF)
Eof.__doc__ = \
  """
  Eof is an RE which matches the end of the file.
  """
Eof.str = "Eof"

